Bathymetry is the science to define the topography of seabed. One of the leading researches in remote sensing of the marine environment is the determination of bathymetry from satellite images. This study provides a method for mapping a shallow lake bathymetry in Al Manzala Lake, Egypt using Sentinel-2A (10m resolution) and Landsat 8 imagery (30m resolution), which are free data sources. The most popular model is linear ratio model that was used to estimate water depth of shallow water bodies. This model was implemented using blue and green bands for Sentinel-2A and Landsat 8 satellites. The computed depths were validated against the in situ measurements. The root mean square errors (RMSE) were calculated for every satellite. We enumerate the error between in situ measured and satellite estimated lake depth value. Our results indicate the high correlation 0.92 between estimated (Sentinel-2A) and in situ depth measurement with RMSE = 0.29 m while low correlation 0.009 when using Landsat-8 with RMSE = 0.817 m. This case study suggests that the Sentinel-2A could retrieve accurate bathymetry information compared to Landsat 8.